As a conventional throttle apparatus which is applied for an engine mounted on an automobile, a wire-cum-electronic controlled type and just an electronic controlled type are known.
For example, with the conventional wire-cum-electronic controlled type throttle apparatus for a six-cylinder V-type engine, the intake system has two surge tanks collecting three intake passages respectively which correspond to each cylinder and intake passages extending to the upstream side from each surge tank. By coupling two throttle valves disposed at each intake passage of the upstream side with one throttle shaft, and driving to open and close by a wire or a motor, the throttle valves are returned to a rest position at the closing side by a return spring disposed around the throttle shaft, for example, as disclosed in Japanese Patent Laid-open H6-207535.
Further, with a conventional electronic controlled type throttle apparatus, one throttle shaft being free to rotate links the two throttle valves which are respectively disposed at two intake passages which are formed in a throttle body. The open-close drive is performed by a motor which is disposed at one end side of the throttle shaft, and the throttle valves are returned to a rest position at the closing side by a return spring which is disposed at the other side of the throttle shaft, for example, as disclosed in Japanese Patent Laid-open H8-218904.
With the abovementioned conventional apparatuses, to return the throttle valves to a rest position at the closing side in a state of rest or emergency etc, a torsion type return spring with relatively large urging force is employed. In the normal open-close operation, the urging force of the return spring acts as a drive load to a motor etc. Therefore, the electric power consumption is increased, and the motor is upsized. Further, the apparatus is upsized as a whole.
The present invention was devised in view of the problems of the related art. The object of the present invention is to provide a throttle apparatus which performs a rapid return operation in the state of rest or emergency, while smoothly achieving an open-close operation by eliminating return force unneeded for a normal open-close operation which was needed conventionally.